Upwardly folding doors are known in the prior art for closing rear openings in vehicles. Some of the known doors have roller tracks to guide folding door travel. Other known doors rely on pivoting linkages for guiding the doors during opening and closing operations.
One known upwardly folding rear door design has a lower door panel that folds inwardly and upwardly toward an upper door panel to gain access to the rear of a vehicle. A dividing hinged shaft connects the upper panel to the lower panel and allows relative movement. In addition, a single pivoting link is attached to each side of the door to guide door travel.
Another known upwardly folding rear door design includes blow molded plastic upper and lower panels connected together by an integrally formed plastic living hinge. A single strut is pivotally attached to each side of the door and connects to an upper part of the upper panel.
Yet another known upwardly folding door has upper and lower panels connected for folding along a horizontal axis. The door has a complex linkage arrangement having a single link pivotally attached on each side of the lower panel, with another pair of linkages pivotally interconnected to the single links and actuated by a power cylinder to automatically control door movement.
However, most known upwardly folding doors are relatively heavy because they have inner and outer structural panels stamped from steel that are hemmed and spot welded along peripheral, flanged edges to form a door. The plastic door mentioned above reduces weight, but sacrifices durability by using a living plastic hinge. Using plastic as a structural component reduces the overall stiffness and strength of the door. Thus, the conventional folding doors do not provide light weight without sacrificing bending stiffness and impact strength.
Further, conventional folding doors have unsatisfactory guiding systems. Some known designs are too complex, using roller tracks and/or several interconnected links having multiple pivot points. The complex designs are costly to produce. Other conventional folding doors have inadequate supports, providing only single links on each side of a door. Thus, the link's pivot points can become over stressed, causing wear, which leads to a loosely guided door.